The present invention relates to a starting fuel supplying apparatus for an engine.
Heretofore, in a starting fuel supplying apparatus for an engine that has been known, there is provided a starting intake passage which bypasses a throttle valve of a carburetor, in order to enhance the efficiency in the cold start of the engine. A starting fuel passage is connected to the starting intake passage. The starting intake passage is provided with a starting valve, and this starting valve is opened and closed by the expansion and contraction of a thermo-sensitive member. At the cold start of the engine, the starting valve is opened by the contracting of the thermo-sensitive member to supply starting fuel from the starting fuel passage, thereby enhancing the efficiency in the cold start of the engine.
An example of such a starting fuel supplying apparatus for an engine is, for example, disclosed in JP-A-07-77059 as a starting fuel supplying apparatus for an outboard motor. The structure thereof is shown in FIG. 5. On a side of an engine 101, a plurality of carburetors 102 are arranged vertically in line in each cylinder of the engine. On the opposite side of the engine 101 across the centers of the carburetors 102, a starting fuel supplying apparatus 103 and a thermo-sensitive member 104 are provided.
There is also known an outboard motor comprising a plurality of carburetors vertically arranged as mentioned above, in which a starting fuel supplying apparatus and plural thermo-sensitive members are provided and the thermo-sensitive member provided in the uppermost carburetor is projected above the engine.
As shown in FIG. 5 above, the thermo-sensitive members are conventionally disposed on the opposite side of the engine across the centers of carburetors, and therefore, it is difficult to conduct the heat generated by the engine at the warm-up tends to the thermo-sensitive members, so that the temperature of the thermo-sensitive members lower faster than that of the engine when the engine is stopped. This makes the starting valve to be opened unnecessarily widely by the thermo-sensitive member cooled off earlier at the warm-up-state restarting of the engine, and could lead to poor restarting caused by over-richness.
Moreover, in the above outboard motor, a link mechanism 106 which links throttle valves of each carburetor 102 is generally disposed on the opposite side to the engine 101, that is, on the side of a cowling 105 as shown in FIG. 5. Thus, when the starting fuel supplying apparatus 103 and the thermo-sensitive member 104 are disposed on the side of the cowling 105 so as not to interfere with the link mechanism 106, there is a problem that the whole carburetor would become large-sized and the cowling, which covers the engine, would become large-sized.
Furthermore, when the thermo-sensitive member attached to the uppermost carburetor is provided to project above the engine, heat retaining property therein is poorer than that in the thermo-sensitive members attached to the lower carburetors, and this provides poor restarting.
Furthermore, in order to prevent the poor restarting caused by the thermo-sensitive member with its temperature lowered faster than the engine, there is disclosed in JP-Y2-02-47253 a starting apparatus, in which a first heat-retaining cover and a second heat-retaining cover made from synthetic resin with low heat conductivity are disposed doubly with a gap therebetween around the thermo-sensitive member, thereby enhancing heat-retaining property and preventing the thermo-sensitive member from cooling.
However, it is impossible to have satisfactory restarting performance because of insufficient heat-restraining property even with such heat-restraining covers. In addition, as the thermo-sensitive member becomes large-sized because of the heat-restraining covers doubly arranged with the gap therebetween, the whole carburetor becomes large-sized. For example, in the case where a large equipping space for the carburetors cannot be secured in the cowling as in the outboard motor or the like, there is a problem that it would be difficult to equip the carburetor or the cowling would become large-sized.
An object of the present invention is to provide a starting fuel supplying apparatus for an engine in which the carburetor is disposed on a side of the engine to solve the above problems.
To attain this object, according to a first aspect of the present invention, there is provided a starting fuel supplying apparatus for an engine in which a carburetor is disposed on a side of a cylinder; wherein the carburetor is provided with a starting fuel supplying apparatus comprising: a starting intake passage communicating a main intake passage while bypassing a throttle valve of the carburetor; a starting fuel passage connected to the starting intake passage; a starting valve adapted to open and close the starting intake passage by moving forward and backward in the starting intake passage; and a thermo-sensitive member connected to the starting valve and adapted to control the opening and closing of the starting valve by its expansion and contraction in accordance with ambient temperature, and the thermo-sensitive member is disposed on the side of the carburetor close to the engine.
In the first aspect, as the thermo-sensitive member is disposed on the side of the carburetor close to the engine, it is easy for the thermo-sensitive member to receive the heat from the engine. Therefore, after the engine stops, the thermo-sensitive member is gradually cooled in accordance with the ambient temperature of the engine, and the starting valve opens gradually in accordance with the falling of the ambient temperature of the engine without opening rapidly. In this way, after the engine stops and in a warm-up state, the starting valve has an opening state appropriate for the temperature of the engine. And at the warm-up restart, as the mixture is prevented from becoming over-rich, satisfactory restarting is performed with richness and amount of the mixture required depending upon the condition of the engine.
According to the second aspect of the present invention, an engine is provided with a plurality of carburetors vertically disposed on a side of a cylinder; wherein the carburetors is provided with a starting fuel supplying apparatus comprising: a starting intake passage communicating a main intake passage while bypassing a throttle valve of the carburetors; a starting fuel passage connected to the starting intake passage; a starting valve adapted to open and close the starting intake passage by moving back and forth in the starting intake passage; and a thermo-sensitive member connected to the starting valve and adapted to control the opening and closing of the starting valve by its expansion and contraction in accordance with ambient temperature, and the thermo-sensitive member being disposed on a side of the carburetors close to the engine, and the thermo-sensitive member disposed in the uppermost carburetor being made to project into a cover that covers the upper part of the engine.
In the second aspect, in the case where a plurality of thermo-sensitive members is vertically arranged on the side of the engine, the thermo-sensitive member in the uppermost carburetor is made to project into the cover that covers the upper part of the engine. As a result, the thermo-sensitive member is kept warm by the hot air in the cover remaining due to the heat generated by the engine. In this way, the thermo-sensitive member is cooled gradually in accordance with the ambient temperature of the engine without cooling off rapidly, and the starting valve is controlled in the same way as the first aspect. In this way, at the warm-up restart, as the mixture is prevented from becoming over-rich, satisfactory restarting is performed with richness and amount of the mixture required depending upon the condition of the engine.
The above and further objects and features of this invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.